The following investigation of the molecular basis of the interaction between the axonal plasma membrane, the myelin membrane and its cell of origin is proposed: perfection of a technique to isolate a myelin fraction which is free of axolemma as well as nodal and internodal axolemmal fractions which are not contaminated with microsomal mitochondrial or myelin membranes. This technique will be appropriately modified to yield membrane fractions of defined purity during all stages of myelinogenesis. The cellular origin of the axolemmal membrane fractions isolated from animals during myelinogenesis will be demonstrated with indirect biochemical and direct morphological evidence. The nature of the molecular forces by which myelin is attached to the axolemma will be investigated. The lipid protein and glycoprotein composition (as determined by binding of labeled lectins) of the axolemmal fractions will be determined during myelinogenesis. The ability of the axolemmal membrane to stimulate glial cell division via a membrane bound "mitogenic signal" will be evaluated during myelinogenesis. Finally, the molecular nature of the mitogenic signal will be determined via the ability of isolated axolemmal molecular components to stimulate glial cell division.